Gas turbine components operate at elevated temperatures requiring active cooling in order to protect the components from harsh environments. Traditionally, gas turbine engine components have been cooled by compressed air or in some instances, by steam available from a combined steam/gas cycle. The use of compressed air for cooling purposes, however, comes at the price of reduced engine performance and efficiency. Thus, the challenge remains to identify ways of reducing coolant flow while maintaining component temperatures within stringent requirements.
Traditionally, temperatures of gas turbine components have been maintained within requirements by convection cooling and thermal barrier coatings. Several techniques are applied to enhance convection heat transfer between the coolant and the internal metal surfaces. Among them, pin-fin banks and turbulators are widely used. In this regard, it is known that heat transfer is reduced as the height of a boundary layer develops and grows. Pin-fin banks and turbulators create a disruption in the boundary layer that allows the boundary layer to restart. Since the boundary layer height is greatly reduced with the restart, heat transfer increases relative to the heat transfer prior to the restart. By adding several pin-fin banks or turbulators, the total heat transfer is increased as compared to a smooth surface. Such heat transfer augmentation devices are well-represented in the patent literature. For example, U.S. Pat. No. 6,464,462 describes the use of splitter ribs on the trailing edge of a bucket for increasing heat transfer. U.S. Pat. No. 6,406,254 describes the use of turbulators on the trailing edge of a nozzle, and U.S. Pat. No. 5,609,466 describes the use of pin-fin banks on the trailing edge of a nozzle.
There remains a need for more effective heat transfer enhancement mechanisms within turbine engine airfoils and particularly in confined, hard-to-access areas of the airfoils such as the internal trailing edge cavities.